Limit switch



June 1, 1948. R. "J. SCHAEDLER 2,442,711

LIMIT swITcH Filed July 24, 1945 2 Sheets-Sheet 1 June 1, 1948. R. J. scHAEnLr-:R 2,442,711

LIMIT SWITCH Filed July 24, 1945 2 Sheets-Shes?.V 2

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45, Serial-1519.4606,731

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Y switch case.

snap ring 46. At its front end the cam has a segmental Yflange 41, extending for about two-Y the vertical wall 32 but separated therefrom by right. The adjusting screw limits the movement to the right, While the resilient contact resists upward movement of the roller upon Vbecoming engaged by the latter. Upon downward move- Yment of the block, the lower roller is urged downwardly and to the right. Y

the back of the switch case, being mounted on` a strip of insulating material 49. The base plate is secured in position by screws 5I. to Figs. 4 and 5 the base. plate 48 has adapted to surround the output shaft 29 and having suiicient diameter'topermit passage of the cam Vflange 41 through the bore. Arranged aboveA and below the bore is a pair of stationary contacts 53 and 54 each consisting of a metal strip bent into U-shape, the web portion being riveted to the'base plate 48 and the right arm being somewhatwider than the left arm. The latter arm-of the stationary contact is attached to an electrical conduct-or 55 orV 56 by soldering. Cooperating with the stationary contacts53 and 54 and normally engaging Iboth of them is a resilient contact 51. The latter consists of a flat metal strip bent into U-shape with the arms arranged to extend horizontally above and below stationary contacts 53 and 54 respectively. The contact member 51 is so constructed that'in its detached Vcondition the `arms thereof tend Vto converge toward the free end, whereas in the assembled condition the parallel arms are held under tension by engagement with the right arms of the stationary contacts 53 and 54. The midportion of the resilient contact 51 has an integral tab 58 rivitedv to the basei48 to hold the resilient contact withrits arms adjacent to spaced from the base plate 48. A conductor 59 is soldered to the resilientV contact 51. 'I'he conductor 59 is normally connected to both con- Referring ductors 55 and `456 simultaneously, but may beV disconnected therefrom by spreading the arms Yof the resilient contact 51 against spring pressure and away from-the respective stationary contacts.

The arms of the resilient contact 51 are sprung, to break the circuit, bythe action of aV pairof cylindrical rollers 6l composed of insulating material. The ends of the rollers abut against the cover jplate 43 and 'base' 48 to prevent axial movement. 'Normally each roller is also con'- iined against more thana slight amount of trans-` a bore 52* IIn order to restrain the block 54 for rectilinear vertical movement, a guide 65 is provided. The guide 'is generally channel shaped, comprising a mid-portion which is riveted to the base 48 and a pair of vertical arms which slidably receive the block therebetween. The left arm is made longer than theright arm as it engages the long side of the block 64 and sustains the reactive thrust exerted on the block by the rollers El.. The right arm, however, Vis thicker than the left and is apertured to receive a pin 65 which extends horizontally through theguide 65, past the base 48 and insulating'strip 49, and into the vertical wall but l'slightly latory movement, being adapted to engage other parts of the switch at three spaced portions of the circumference of the roller.'` Referring to the upper roller` 6|, the top of the roller` underlies the resilient 'contact 51, and the right side lies adjacent to the abutting end of an adjusting screw 82 extending through the peripheral wall of the The screw is `'secured in Vadjusted position by a lock nut 63. Near the bottom and toward the left the roller lies adjacent the inclined surface of a sliding block 64; When viewed as in Figs.V 1, 2, 3, 12 and 13, the block has'ithe shape` of an isosceles trapezoid with its largest side on the left. yThe lower roller V6| is similarly face of the block, that is, upwardly'and to the 32'which defines the back of the switch case. Upon the pin is ful-crumed a lever or trigger 61, which consists of a flat stamping having a butt end on its right side near the fulcrum and having a reduced portion 68 at its opposite end. The lever swings vwithin vertical slots 59 and 1| provided in the left and right armsrespectively of the channel guide 65.V the lever projects into the recess in the segmental flange 41 on cam d5, whereby the lever may be lifted` as the cam approaches the limit vposition ofl Fig. 1, or depressed as the cam approaches the opposite limit position of Fig. 3. VThe lever is biased towardV its normal or central position by means of a flat leaf spring 12 having one arm engaging the butt end of lever 61V and the other arm resting against a recessed portion of the peripheral wall I9 of the switch case. As the lever is lifted or depressed it raises or lowers the sliding block 64. To this end the block is provided with a revolves counterclockwise, moving the air control flap 4| to closed position. At the same time the cam 45 turns counterclo'ckwisebut without any .immediate effect upon the other parts ofthe switch as the resilient contact 51 remains in engagement with the stationary contacts 53 and 54. Referringto the wiring diagram of Fig. 15 current flows from a battery wire 15 through upper set of contacts of manual switch 15, conductor 11, forward motion relay 18, conductor 55, upper stationary contact 53, resilient contact 51 Vand conductor 59to ground. The relay 18 being energized, acts through its armaturesv to connect the motor 20 through a set of conductors alto a source of three-phasel current 82.Y

The motor continues to drive the output shaft 29 until the lever arm l31'approaches the full line` position of Fig. 1. Up to this time the cam 45 hasV been turning withY lost motion relative l to the Y .lever lprojecting within the Vrecess in the cam. VUpon approach of the limit position, however,

the abutment at one end of the segmental flange Y 41 engages the projecting end 68 of lever 61,

lifting the lever about the vpivot pin 5B, which in 64 ln the channel guide turn lifts the sliding block The reduced end 68 of;

responsive tomovementfof the blockaway .from normal position toactuate a contact member..

2. An electric` switchf according-to claim! 1- in which the? last mentioned means has an adjustable amount of lost motion to vary the extent of movement of the cam, lever and block required for the actuation of the contact member.

3. An electric switch comprising a non-conductive base plate, upperand lower stationary contacts mounted on the base platel a resilient contact having approximately parallel horizontal arms normally tensioned apart by engagement with the stationary contacts, and means for selectively forcing thevarm's farther part under additional tension to disengage the stationary contacts, said means comprising a cam positioned between said arms to rotate on an aXis perpendicular to the base plate, a pair of circumferentially spaced abutments on the cam, a triggerY positioned between the abutments and Vengageable thereby upon predetermined movement ofthe cam in either direction, a sliding block mounted to move transversely to the parallel arms near'the free ends thereof, the block being movable vertically by the trigger and being arranged to force the resilient contact out of engagement with the ,stationary-contact upon predetermined movement of the block.

4. In an electric switch, a case having front' and rear walls, a horizontal shaft extending through the rear wall, a cam mounted-on the shaft, a guide supported on the rear wall and having a channel open at its front end and extending vertically and tangentially to thecam, a block slidably mounted in the channel guide, a contact member extending horizontally and above the block, the-upper end of the block having an inclined surface extending downwardly and Vtoward a peripheral wall of the switch'casaa roller interposedl between the sliding block `and contact member'y a stop means supported by said Aperipheral Wall for limiting movement of the roller toward the latter, said stop means, contact member and block normally being suiiiciently spaced to permit a predetermined amount of `upward lost motion of the block before the roller is simultaneously engaged by the block and the contact member and the stop means, following which lost motion theV continued upward movement of the block is transmitted to the vcontact member forY raising it from its normal position.

5. An electric switch accordingto claim 4 in which the stop means is adjustable toward and away from the peripheral wall to regulate the eX- tent of lost motion, and is connected to a manipulative adjusting screw extending through the peripheral wall, whereby adjustment may be effected without opening the switch case.

6. In an electric switch, a case having front and rear walls and a peripheral wall, a horizontal shaft extending through the rear walL-a Tcam enclosed within the oase and mounted on the shaft, ,a block slidably mounted for vertical movement in the case and actuated by the cam, a contact member in the case extending horizontally above the guide block, a oating element interposed between the sliding block and contact member, a stop means supported adjacent said peripheral wall for limiting lost motion of the fioating element, said stop means being adjustable to regulate the extentY of lost motion, and a manipulative adjusting screw Vextending Ythrough kthe pe- Vmined deection of the lever ripheral wall and.l operatively connected to the stop means,'whereby the switch may be ladjusted without opening the switch case. *A

v7. VAn electric switch comprising a casing, an output shaft rotatable therein without interruption to a limit position in either direction, a cam rotatable with said shaft and having a circumferential flange recessed to provide spaced abutments at opposite ends of the recess, a lever pivotally supported in the casing and positioned to be reciprocably actuated by said abutments, resilient means biasing the lever toward a normal position radially of the cam, a sliding block adapted to be vmoved in opposite directions by the reciprotending through the casing adapted to adjustrtheV position of the floating roller or rollers relative to the sliding block to predetermine the lost motion between said block and contact member and hence the amount of movement of the lever required to modify the electric current.

.8. A limit switch comprising a switch case, a cam supported therein for rotary movement proportionately to a power-shaft, a segmental flange onthe cam forming a circumferential `recessbetween two spaced abutmentsv a lever pivotally mounted in the switch case and having a project-v ing portion extending into the cam recess'thereby being operable by one of said shoulders following a predetermined rotation of the cam, the lever being biased toward a normal position radially of the cam, and means responsive to a predeteraway from normalL position for modifying an electric circuit,` said means comprising a sliding block actuated bythe lever, a U-shaped resilient contact member having parallel arms extending on opposite sides'of the block and transverse to the direction of movementY thereof, a non-metallic roller at each end of the block adapted to transmit force from the block to the `contact member, and means for adjusting the position of a roller or rollers relative to the block to vary the lostY motion between the block and contact member and hence the amount of movement ofY the modifying the electric circuit; d

Y RAYMOND J.. SCHAEDLER.

REFERENCES CITED 'f The following refere file of thisv patent:

UNITED STATES PATENTS ces are of record Vin the Chapman i Sept. 10, 1946 cam and lever required'for K 

